import Tkinter
from Tkinter import *

#creates an object of type frame from Tkinter
class Application(Frame):
    
    #starting this application with these available to use
    def __init__(self, master):
        Frame.__init__(self, master)
        self.grid() #extremely useful, used for placement of widgets
        self.create_widget() #same as above but for creation instead of placement


    #this is where all of our widget objects go,  and most of our code.
    #seems tedious but does the job.
    def create_widget(self):
        #an Entry object lets us type in it, and then pull info from it
        #sticky just makes the widget object fit inside the placement box
        #based on the directions specified N-orth S-outh E-ast W-est
        self.num_1 = Entry(self)
        self.num_1.grid(row = 1, column = 3, sticky = W)
        
        self.num_2 = Entry(self)
        self.num_2.grid(row = 2, column = 3, sticky = W)

        #creates a Label widget based on a global variable I define later
        if this_fun == function[0]:
            self.inst_lbl = Label(self, text = "+___________________")
            self.inst_lbl.grid(row = 3, column = 3, sticky = W)
        elif this_fun == function[1]:
            self.inst_lbl = Label(self, text = "-____________________")
            self.inst_lbl.grid(row = 3, column = 3, sticky = W)
        elif this_fun == function[2]:
            self.inst_lbl = Label(self, text = "x___________________")
            self.inst_lbl.grid(row = 3, column = 3, sticky = W)
        else:
            self.inst_lbl = Label(self, text = "/___________________")
            self.inst_lbl.grid(row = 3, column = 3, sticky = W)

        
        #create submit button,  you will notice something new about this, the command
        #variable.  very handy and we shall use more later
        self.submit_bttn = Button(self, text = "         =         ", command = self.reveal)
        self.submit_bttn.grid(row = 3, column = 0,columnspan = 2, sticky = W+E)
        #used to change the Label string and value of global "this_fun"
        self.submit_bttn = Button(self, text = "     +    ", command = self.add)
        self.submit_bttn.grid(row = 1, column = 0, sticky = W+E)

        self.submit_bttn = Button(self, text = "     -    ", command = self.subtract)
        self.submit_bttn.grid(row = 1, column = 1, sticky = W+E)

        self.submit_bttn = Button(self, text = "     x    ", command = self.multiply)
        self.submit_bttn.grid(row = 2, column = 0, sticky = W+E)

        self.submit_bttn = Button(self, text = "     /    ", command = self.divide)
        self.submit_bttn.grid(row = 2, column = 1, sticky = W+E)

        #Time for a new type of object,  the Check Buttons
        #for these we need a boolean variable we can change
        self.use_again = BooleanVar()
        Checkbutton(self,
                    text = "Use equated value for next calculation",
                    command = self.place_it
                    ).grid(row = 5, column = 0, columnspan = 3, sticky = W+E)
        

    
        #create a display Widget width for num of characters per line
        #height for lines of characters, wrap does well..... wrap kinda like
        #notepad would.  very handy
        self.secret_txt = Text(self, width = 20, height = 1, wrap = WORD)
        self.secret_txt.grid(row = 4, column = 3,sticky = W)

    def place_it(self):
        global use_num
        use_num = self.calculate_int()

    def calculate_int(self):
        if this_fun == function[0]:
            done_val = int(self.num_1.get()) + int(self.num_2.get())
            return int(self.num_1.get()) + int(self.num_2.get())
        elif this_fun == function[1]:
            done_val = int(self.num_1.get()) - int(self.num_2.get())
            return int(self.num_1.get()) - int(self.num_2.get())
        elif this_fun == function[2]:
            done_val = int(self.num_1.get()) * int(self.num_2.get())
            return int(self.num_1.get()) * int(self.num_2.get())
        else:
            done_val = int(self.num_1.get()) / int(self.num_2.get())
            return int(self.num_1.get()) / int(self.num_2.get())

    def reveal(self):
        msg = str(self.calculate_int()) + "  this_fun =" + this_fun + " " + str(use_num) 
        self.secret_txt.delete(0.0, END)
        self.secret_txt.insert(0.0, msg )

    def add(self):
        global this_fun
        self.inst_lbl = Label(self, text = "+___________________")
        self.inst_lbl.grid(row = 3, column = 3, sticky = W)
        this_fun = function[0]
    def subtract(self):
        global this_fun
        self.inst_lbl = Label(self, text = "-____________________")
        self.inst_lbl.grid(row = 3, column = 3, sticky = W)
        this_fun = function[1]
    def multiply(self):
        global this_fun
        self.inst_lbl = Label(self, text = "x___________________")
        self.inst_lbl.grid(row = 3, column = 3, sticky = W)
        this_fun = function[2]
    def divide(self):
        global this_fun
        self.inst_lbl = Label(self, text = "/___________________")
        self.inst_lbl.grid(row = 3, column = 3, sticky = W)
        this_fun = function[3]



function = ["+","-","x","/"]
this_fun = function[0]
use_num = 0
done_val = 0


root = Tk()
root.title("Simple Calculator")
root.geometry("400x200")

app = Application(root)
root.mainloop()